Fix build of Mips code with MSVC by using our macro instead of __attribute__((unused)) directly

llvm-svn: 221956
diff --git a/llvm/lib/Target/Mips/MipsFastISel.cpp b/llvm/lib/Target/Mips/MipsFastISel.cpp
index ad31ef8..2bb16e3 100644
--- a/llvm/lib/Target/Mips/MipsFastISel.cpp
+++ b/llvm/lib/Target/Mips/MipsFastISel.cpp
@@ -180,7 +180,7 @@
 
 static bool CC_Mips(unsigned ValNo, MVT ValVT, MVT LocVT,
                     CCValAssign::LocInfo LocInfo, ISD::ArgFlagsTy ArgFlags,
-                    CCState &State) __attribute__((unused));
+                    CCState &State) LLVM_ATTRIBUTE_UNUSED;
 
 static bool CC_MipsO32_FP32(unsigned ValNo, MVT ValVT, MVT LocVT,
                             CCValAssign::LocInfo LocInfo,